A Modality is querying a PACS / HL7 broker for the MWL. Upon each query the PACS provides a unique Study ID based on the query time. When the Modality re-queries the same appointment again a different unique Study Instance UID is provided.

The PACS is using the DCMTK. Is there any documentation pertaining to the workflow of the PACS in regards to providing the same Study UID throughout the life of the Appointment?. The problem arrises when the modality receives a different study instance UID from original and any manually entered information on the work list screen is lost.

Should the PACS be providing the same Unique Study ID upon a MWL re-query? Trying to find some information pertaining to this standard if there is one.

The DCMTK worklist server does perform correctly -- if used correctly (i.e. the worklist files for a specific scheduled procedure step should already contain the Study Instance UID). If it does NOT contain one, the worklist server may work incorrectly: Then it answers a request for a Study Instance UID every time with a new UID. Therefore, let's say (this is an alibi...), DCMTK's worklist server does not prohibit wrong usage, which is not a good behaviour. Instead it should be maybe extended that it remembers the Study Instance UID it sent out once for a specific worklist entry. We are aware of that but we cannot promise any fix in the near future (lack of time).